1. Field of the Invention
This invention relates to an optical code reader for reading a 2-dimensional code affixed to an article, and more particularly to an optical code reader which can be held by hand and set close to the 2-dimensional code at the time of reading.
2. Description of the Related Art
Most supermarkets utilize bar codes printed on article labels for sales registration. The bar code represents an article code by a combination of bars linearly arranged and is optically read by a handy type bar code scanner which can be held by hand and set close to and substantially in contact with the bar code at the time of reading, for example. In recent years, the application fields of bar codes are expanding to factories, distribution industries, service businesses and the like. In these application fields, it is necessary to express article information other than the article code by use of bar codes for the article management. Therefore, the recording capacity of bar codes tends to become insufficient. In this condition, 2-dimensional codes such as multi-bar codes and matrix array codes are developed to treat a large amount of article information.
The conventional 2-dimensional code scanner is constructed by connecting a TV camera, TV monitor and image processing device via cables, for example. The TV camera takes an image of a 2-dimensional code printed on the article label under the interior lighting, the TV monitor displays the image of the 2-dimensional code taken by the TV camera, and the image processing device effects an image process of deriving article information from the image of the 2-dimensional code. For example, the article information is transferred to an exterior host computer connected to the image processing device via a communication circuit.
However, the 2-dimensional code scanner is large, heavy and expensive. Further, the operator is required to set the article label in position perpendicular to the optical axis of the TV camera and must adjust the focus of the TV camera according to the distance between the TV camera and the label and adjust the aperture of the TV camera according to the brightness of the interior lighting. This makes the start of reading delayed. It is considered that the above problem can be solved by constructing the 2-dimensional code scanner so as to be set close to and substantially in contact with the label like the handy type bar code scanner.
Since the 2-dimensional code scanner interrupts the interior lighting when it is set close to the 2-dimensional code, it is necessary to provide an illumination light source for illuminating the 2-dimensional code instead of the interior lighting. It is preferable to activate the illumination light source only for an operation period of a reading circuit driven by operation of a trigger switch, for example, since the power consumption can be lowered. However, the 2-dimensional code cannot be read when the 2-dimensional code is set partly out of the reading range. If the operation period of the reading circuit is set to be relatively long so as to provide sufficient time for correcting the position of the 2-dimensional code, it becomes impossible to rapidly read a large number of 2-dimensional codes. Further, if the operation period of the reading circuit is changed according to the period in which the trigger switch is kept depressed, much attention must be paid to the operation of the trigger switch so as not to interrupt the reading operation.